Systems and methods for removing micro-particles from a metalworking fluid

Abstract

A method of removing metal particles from a contaminated metalworking fluid comprising emulsion droplets and metal particles includes pressurizing a first clean metalworking fluid with gas to provide an aerated metalworking fluid; releasing the pressure of the aerated metalworking fluid to form a plurality of bubbles; applying a shear force to the contaminated metalworking fluid to separate the emulsion droplets from the metal particles; flowing the contaminated metalworking fluid with the aerated metalworking fluid in a laminar flow to form a combined fluid, wherein the flowing occurs during the formation of the plurality of bubbles and while the emulsion droplets are separated from the metal particles, and wherein the laminar flow lasts for a time sufficient for the plurality of bubbles to attach to the metal particles; releasing the combined fluid into a flotation tank; and removing the metal particles to form a second clean metalworking fluid.

I claim: 
     
       1. A method for removing metal particles from a contaminated metalworking fluid comprising emulsion droplets and metal particles, the method comprising:
 pressurizing the contaminated metalworking fluid with gas in a pressurization vessel to provide an aerated metalworking fluid; 
 flowing the aerated metalworking fluid from the bottom of the pressurization vessel to a coagulation channel; 
 applying a shear force to the aerated metalworking fluid to separate the emulsion droplets from the metal particles; 
 reducing the pressure of the aerated metalworking fluid to provide a plurality of bubbles, wherein the reducing the pressure occurs after applying the shear force and while the emulsion droplets are separated from the metal particles; 
 flowing the aerated metalworking fluid in a laminar flow through the coagulation channel to a floatation tank, wherein the laminar flow lasts for a time sufficient for the plurality of bubbles to attach to the metal particles; 
 releasing the aerated metalworking fluid into the flotation tank; and 
 removing the metal particles to provide a clean metalworking fluid. 
 
     
     
       2. The method of  claim 1 , wherein the reducing the pressure is 0.5 second or less after applying the shear force. 
     
     
       3. The method of  claim 1 , wherein the shear force is a mechanically generated shear force. 
     
     
       4. The method of  claim 1 , wherein the time sufficient for the plurality of bubbles to attach to the metal particles is at least 1.0 second. 
     
     
       5. The method of  claim 1 , wherein at least one of (i)-(iii) applies:
 (i) the metal particles have an average particle size of 30 micron or less; 
 (ii) metal particles are non-ferrous; or 
 (iii) the metal particles comprise one or more of copper, aluminum, nickel, lead, titanium, tungsten and molybdenum. 
 
     
     
       6. The method of  claim 1 , wherein the clean metalworking fluid is pressurized with gas at 3.5 bar to 6.2 bar for about two minutes or longer. 
     
     
       7. The method of  claim 1 , wherein the aerated metalworking fluid and the contaminated metalworking fluid are flowed in a flow ratio in a range of 1:5 (v:v) to 1:1 (v:v). 
     
     
       8. The method of  claim 1 , wherein the gas comprises atmospheric air or the gas is selected from nitrogen, oxygen, and ozone. 
     
     
       9. The method of  claim 1 , wherein the contaminated metalworking fluid comprises:
 (i) an anionic emulsifier, 
 (ii) a nonionic emulsifier, or 
 (iii) an anionic emulsifier and a nonionic emulsifier. 
 
     
     
       10. The method of  claim 9 , wherein the nonionic emulsifier of (iii) is present at 0.1% wt. to 20% wt of the anionic emulsifier. 
     
     
       11. The method of  claim 1 , wherein the bubbles have a size in a range of 10 microns to 50 microns. 
     
     
       12. The method of  claim 1 , wherein the contaminated metalworking fluid is an oil-in-water phase emulsion. 
     
     
       13. The method of  claim 12 , wherein the emulsion of (i) comprises emulsion droplets having a size in a range of 10 microns to 1 micron. 
     
     
       14. The method of  claim 1 , wherein the contaminated metalworking fluid is a water-in-oil phase emulsion. 
     
     
       15. The method of  claim 1 , wherein the metalworking process is a metal forming or metal removal process. 
     
     
       16. The method of  claim 1 , wherein the coagulation channel is substantially straight. 
     
     
       17. The method of  claim 1 , wherein the amount of emulsifier in the clean metalworking fluid is within 0.1% v/v to 15% v/v of the amount of emulsifier in the contaminated metalworking fluid.